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/model-pin-gate

PreToolUse guard: unpinned Fable-seat spawns and sub-apex Fable targets block. Triggers: model pin, Fable seat, spawn.

$ golems-cli skills install model-pin-gate

Updated 2 weeks ago

Every non-Cursor spawn pins its model explicitly (canon #5); a non-default model such as Fable is used only by explicit per-invocation selection, never inherited. Routing: see /agent-routing § Routing rules (SSOT).

What It Is

model-pin-gate is a Claude Code PreToolUse hook for Task|Agent|Workflow and, with the prepared settings matcher, cmux spawn_agent, dispatch_to_agent, and repoGolem-style new_split launches. It reads the current session's recent assistant model from transcript_path with a bounded tail read. It also honors explicit apex-seat identifiers (orchestrator, orc, skillcreatorLead) when a caller deliberately targets Fable.

The hook enforces Etan's fleet model policy:

Spawn surface	Verdict
`Agent` or `Task` without `tool_input.model`	BLOCK: `MODELPIN_AGENT_UNPINNED`
`Agent`, `Task`, or `Workflow` explicitly targeting Fable from a non-apex seat	BLOCK: `MODELPIN_FABLE_BELOW_APEX`
cmux `spawn_agent`, `dispatch_to_agent`, or `new_split` targeting Fable from a non-apex seat	BLOCK: `MODELPIN_CMUX_FABLE_TARGET`
explicit Fable target from `orchestrator`, `orc`, or `skillcreatorLead`	PASS
explicit non-Fable model (`opus`, `sonnet`, `haiku`, or another explicit non-Fable model)	PASS
`Workflow` script with `agent(` calls and fewer `model:` pins than `agent(` calls	ADVISORY: `MODELPIN_WORKFLOW_AGENT_MODEL_ADVISORY`
`Workflow` script with unpinned `agent(` calls, after `WEEKLY_RESET_AT` (2026-09-06T02:05Z = ~05:05 IDT, Etan 8A)	FLAG: `MODELPIN_WORKFLOW_AGENT_UNPINNED`
`Workflow` script pins Fable, apex seat, before `WEEKLY_RESET_AT`	ADVISORY: `MODELPIN_FABLE_IN_WORKFLOW` (Etan 2026-09-05 amnesty)
`Workflow` script pins Fable, any seat, after `WEEKLY_RESET_AT`	FLAG: `MODELPIN_FABLE_IN_WORKFLOW` (07-18 law)
`Agent`/`Task` pins Fable from an apex seat, before / after `WEEKLY_RESET_AT`	ADVISORY / FLAG: `MODELPIN_FABLE_SUBAGENT`
`Agent`/`Task`/`Workflow` targets Fable from a non-apex seat (any date)	FLAG: `MODELPIN_FABLE_BELOW_APEX`
`Workflow` script with enough `model:` pins	PASS
unrelated tools, malformed payloads, missing/undetectable seat model	PASS fail-open

The Workflow path is intentionally heuristic and advisory-only. It counts agent( occurrences versus model: occurrences and does not attempt full JavaScript parsing inside a 500ms hook.

Hook Contract

Input is the Claude Code PreToolUse stdin payload:

{
  "hook_event_name": "PreToolUse",
  "transcript_path": "/path/to/transcript.jsonl",
  "tool_name": "Agent",
  "seat_id": "skillcreatorWorker",
  "tool_input": { "model": "opus", "prompt": "..." }
}

Output schema:

allow: {}
block: {"decision":"block","reason":"..."}
advisory: {"systemMessage":"..."}

The hook is local-only: no network, no BrainLayer, no subprocesses, bounded stdin/transcript reads, and fail-open on malformed input or internal errors.

install-snippet.json pins the absolute Node path: $HOME/.nvm/versions/node/v22.22.0/bin/node.

Run It

bun test skills/golem-powers/model-pin-gate/evals/model-pin-gate.test.mjs
python3 skills/golem-powers/model-pin-gate/evals/run_suite.py

Programmatic: import { detectModelPin } from "./src/model-pin-gate.mjs" → detectModelPin(payload) returns { verdict, seatModel, tool, violations, advisories }.

Full SKILL.md source — includes LLM directives, anti-patterns, and technical instructions stripped from the Overview tab.